Stabilizing hypochlorite solutions



Patented Dec. 15, 1953 UNE'E'EE STATES ram orr ca STABILIZING HYPOCHLORITE SOLUTIONS Richard 0. Brandon, Elizabeth, N. J., assignor to pment Company, a cor- Standard Oil Develo poration of Delaware 1 Claim. 1

This invention relates to the stabilization of hypochlorite solutions. More particularly, it relates to the stabilization of alkali metal hypochlorites in the presence of metals. Solutions of alkali metal hypochlorites are useful as household bleaches, disinfectants, and in the refining of petroleum distillates.

It is well known that hypochlorite solutions deteriorate upon standing after their preparation, particularly when stored in iron or steel vessels. This instability is attributable to the displacement of unstable hypochlorous acid from its salts. However, it has been the practice to maintain the hypochlorite solution strongly alkaline in order to avoid this decomposition. Furthermore, for some uses, such as in the refining of petroleum distillates, it is desirable to maintain the alkalinity of the solution high. While the presence of excess caustic prevents the displacement of hypochlorous acid, the alkali metal hypochlorite also undergoes decomposition according to the following equation:

Even in strongly alkaline solutions suitable for the refining of petroleum distillates containing 100-250 grams of NaOI-I and 2-12 grams of NaOCl per liter, the solution decomposes showing that it is unstable even at high pH values.

This latter reaction is particularly accelerated by the presence of heavy metals, such as iron or steel, in which the hypochlorite may be stored. In fact this decomposition of NaOCl has been used as a preparative method for oxygen in the laboratory.

It has now been found that the decomposition of alkali metal hypochlorite solutions can be inhibited by adding thereto small quantities of potassium dichromate.

Potassium dichromate may be used in amounts varying from 0.001 to 1% by the weight of the hypochlorite solution. The preferred range is between 0.01 and 0.1%. However, these concentrations are by no means critical. It is obvious that high concentrations provide more stabilization but increase the cost of the product.

The following examples are intended to illustrate the present invention, but in no way to limit it to reagents, proportions, or conditions described therein.

EXAMPLE I Samples of sodium hypochlorite with and without the addition of potassium dichromate were stored in glass at 125 F. in contact with iron strips. The following results were obtained:

Uninhibited Inhibited Solution Solution Initial Composition:

Caustic, g./l 9.0 9.0

Potass1um dichromate, g None 0. 10 Periodic Tests for Hypochlorite After one week 13. 4 22. 5

After two weeks... 6. O 14. 2

After three weeks. 3. 3 10. 4

After four weeks. 2. 4 8. 1

The above data show the solutions containing potassium dichromate were more stable than the same hypochlorite not containing stabilizer.

EXAMPLE II Samples of hypochlorite containing a large excess of sodium hydroxide with and without the; addition of potassium dichromate were tested in! the same manner as Example I, and the following; results were obtained:

containing potassium dichromate were more stable than those to which potassium dichromate was not added.

EXAMPLE III A fraction of West Texas crude containing 47 mgs. of mercaptan sulfur per ml. was mixed with 15% by volume of hypochlorite solution containing 198 g. of caustic per liter and 8.9 g. of of hypochlorite per liter. A similar sample was treated with 15% by volume of the same hypochlorite solution containing 0.5 gram of potass ium dichromate per liter as a stabilizing agent. In both cases, after two minutes, a product was obtained which passed the usual doctor test indicating that all the mercaptan sulfur had been converted. Similar treating with smaller volumes of the same hypochlorite solutions failed to give sweetened products in two minutes. The sweetening activity of the hypochlorite solution containing the potassium dichromate was not affected by the presence of this stabilizer.

The natur and meet of IJIQ QQQ iny n: tion having been thus iully set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

A stabilized aqueous mchlqrite solution consisting of 100-250 grains per liter 0; sodium hydroxide, 2-12 grams per liter of hypg chlorite, and as a stabilizing agent 0:91 to 0.1% potassium dichromate based on the hypochlorite.

RICHARD C. BRANDGN.

4 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 837,655 Armstrong Dec. 4, 1906 1,435,824 Dunstan Nov. 14, 1922 2,022,942 Schulze et a1 Dec. 3, 1935 2,064,541 Hershman Dec. 15, 1936 2,091,186 Reichert et al Aug. 24, 1937 2,333,916 Campbell et a1. Nov. 9, 1943 EQRE N rmws Number Country. Date 94,198 Switzerland Apr. 17, 1922 OTHER REFERENCES Bleaching 8; Related. Process-Matthewspublished by, Chemical Catalog Go, 1110., N. Y.-- Pesss nt- 1% ease 

